Direct fuel injection systems provide some advantages over port fuel injection systems. For example, direct fuel injection systems may improve cylinder charge cooling so that engine cylinder's may operate at higher compression ratios without incurring undesirable engine knock. However, direct fuel injectors may not be able to provide a desired amount of fuel to a cylinder at higher engine speeds and loads because the amount of time a cylinder stroke takes is shortened so that there may not be sufficient time to inject a desired amount of fuel. Consequently, the engine may develop less power than is desired at higher engine speeds and loads. On the other hand, port injected engines may provide a sufficient amount of fuel to a cylinder at higher engine speeds because the port injector may be open from intake valve closing timing of one cylinder cycle to intake valve closing time during a next cylinder cycle. However, port fuel injection tends to provide considerably less cylinder charge cooling as compared to directly fueling a cylinder because of the port fuel injector's location and because the lower fuel injection pressure of port injected fuel may result in less effective fuel vaporization. Thus, there may be opportunities to improve port and directly fueled engines.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for fueling a cylinder, comprising: activating a port fuel injector in response to a request to inject a fuel amount into a cylinder during a cylinder cycle while engine speed is greater than a threshold engine speed at which a direct fuel injector may supply the fuel amount during a predetermined crankshaft interval.
By activating a port fuel injector during a cylinder cycle in response to a request to inject a fuel amount into a cylinder during a cylinder cycle that is greater than a threshold amount while engine speed is greater than a threshold engine speed at which the direct fuel injector may supply the fuel amount during a predetermined crankshaft interval, it may be possible to provide the technical result of increasing fuel flow to the cylinder so that the cylinder may provide additional torque as compared to if only the direct fuel injector is operated. Further, by supplying fuel to the port fuel injector via a high pressure pump, it may be possible to provide additional cylinder charge cooling, thereby providing increased engine torque.
The present description may provide several advantages. Specifically, the approach may reduce engine air-fuel errors. Additionally, the approach may allow an engine to achieve power levels that might not be achievable by a direct fuel injection only fuel system. Further, the approach may improve engine fuel economy.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.